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Antistreptolysin O in the serum
Medical expert of the article
Last reviewed: 04.07.2025
Reference values for antistreptolysin O (ASLO) in blood serum: adults - less than 200 IU/ml, children - up to 150 IU/ml.
Infections caused by group A streptococci always cause a specific immune response - a significant increase in the titer of antibodies to at least one of the extracellular streptococcal antigens - streptolysin O, deoxyribonuclease B, hyaluronidase or nicotinamide adenine dinucleotidase.
ASLO - antibodies against streptococcal hemolysin O. ASLO is a marker of acute streptococcal infection. The concentration of ASLO increases in the acute period of infection (7-14 days) and decreases during the period of convalescence and recovery. In clinical practice, the determination of ASLO is used to monitor the dynamics of the rheumatic process. The ASLO titer increases in 80-85% of patients with rheumatic fever. A persistent significant increase in ASLO activity is of diagnostic value. By the 3rd week of rheumatism, the titer increases significantly, reaching a maximum by the 6-7th week. With a favorable course of the process, the concentration of ASLO decreases to normal by the 4-8th month. Under the influence of the therapy, these periods may be reduced. The absence of a decrease in the concentration of ASLO by the 6th month of the disease suggests the possibility of a relapse. A persistent and long-term increase in activity after tonsillitis may be a harbinger of the rheumatic process. In 10-15% of cases of rheumatism, an increase in the concentration of ASLO is not detected.
An increase in ASLO is found in some patients with rheumatoid arthritis, but the level of its increase in this disease is lower than in rheumatism. When isolating β-hemolytic streptococci of group A, increased ASLO titers are detected in 40-50% of carriers.
An increase in ASLO titers is found in half of patients with acute glomerulonephritis developing after a streptococcal infection.
In most cases, acute rheumatism or acute poststreptococcal glomerulonephritis develops within 1 week to 1 month from the onset of infection; the average latent period is 18 days for rheumatism, 12 days for glomerulonephritis after a throat infection, and up to 2-3 weeks after skin infections. Therefore, it is most likely to detect an increase in the concentration of ASLO and other antibodies in the first 2-3 weeks from the onset of the disease.
Cutaneous streptococcal infections often result in low ASO production, probably due to the ASO inhibitory effects of cholesterol and a number of skin-associated lipids.
It should always be remembered that taking antibiotics during the acute phase of streptococcal infection significantly reduces the severity of the immune response, and the increase in the concentration of ASLO may be insignificant.
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